fix: Change SOVERSION to <major>.<minor> for 2.x release versions

diff --cc CMakeLists.txt
index 68f9ea3,8e9e315..14cdb90
--- 1/CMakeLists.txt
--- 2/CMakeLists.txt
+++ b/CMakeLists.txt
@@@ -106,27 -34,7 +106,32 @@@ version_numbers 
      PACKAGE_VERSION_PATCH
  )
  
 -set (PACKAGE_SOVERSION "${PACKAGE_VERSION_MAJOR}.${PACKAGE_VERSION_MINOR}")
 +# shared library ABI version number, can be overridden by package maintainers
 +# using -DGFLAGS_SOVERSION=XXX on the command-line
 +if (GFLAGS_SOVERSION)
 +  set (PACKAGE_SOVERSION "${GFLAGS_SOVERSION}")
 +else ()
-   set (PACKAGE_SOVERSION "${PACKAGE_VERSION_MAJOR}")
++  # TODO: Change default SOVERSION back to PACKAGE_VERSION_MAJOR with the
++  #       next increase of major version number (i.e., 3.0.0 -> SOVERSION 3)
++  #       The <major>.<minor> SOVERSION should be used for the 2.x releases
++  #       versions only which temporarily broke the API by changing the default
++  #       namespace from "google" to "gflags".
++  set (PACKAGE_SOVERSION "${PACKAGE_VERSION_MAJOR}.${PACKAGE_VERSION_MINOR}")
 +endif ()
 +
 +# when gflags is included as subproject (e.g., as Git submodule/subtree) in the source
 +# tree of a project that uses it, no variables should be added to the CMake cache;
 +# users may set the non-cached variable GFLAGS_IS_SUBPROJECT before add_subdirectory(gflags)
 +if (NOT DEFINED GFLAGS_IS_SUBPROJECT)
 +  if ("^${CMAKE_SOURCE_DIR}$" STREQUAL "^${PROJECT_SOURCE_DIR}$")
 +    set (GFLAGS_IS_SUBPROJECT FALSE)
 +  else ()
 +    set (GFLAGS_IS_SUBPROJECT TRUE)
 +  endif ()
 +endif ()
 +
 +# prefix for package variables in CMake configuration file
 +string (TOUPPER "${PACKAGE_NAME}" PACKAGE_PREFIX)
  
  # ----------------------------------------------------------------------------
  # options